Conventionally, electronic components have been joined and mounted onto a substrate, e.g., a printed circuit board with bonding metal such as solder in widespread application. However, if a large external force is likely to be applied to an electronic component, only a solder joint on the electronic component may not have sufficient bonding strength.
As shown in FIGS. 28 and 29, a solution to this problem is to apply reinforcing resin 54 along the side of an electronic component 52 that is not only bonded to a substrate 53 with solder (solder balls in FIG. 28) 51, but also allows the reinforcing resin 54 to bond the electronic component 52 onto the substrate 53 with reinforced holding power at a joint (for example, Japanese Patent Laid-Open No. 2010-129902). In the reinforcing structure, the reinforcing resin 54 is applied to the corners of the electronic component 52, e.g., a BGA that has a low profile from the substrate 53 with a flat and rectangular shape. The reinforcing structure can satisfactorily reinforce the corners of the electronic component 52 where stress concentration is likely to occur relative to an external force, achieving a remarkably improved reinforcing effect. Advantageously, the reinforcing structure can easily respond to a change of the shape or size of the electronic component 52 only by changing the position of application of the reinforcing resin 54.
Although this reinforcing method is effective for the low-profile electronic component 52, e.g., a BGA, if the method is applied to a large electronic component 56, e.g., a large capacitor or transformer that is relatively thick in profile from the substrate 53 and is relatively heavy as shown in FIGS. 30A to 30C, for example, large vibrations a may concentrate a stress b at a joint 55 between the reinforcing resin 54 and the substrate 53, resulting in an insufficient reinforcing effect. In other words, in the case of the large electronic component 56, the reinforcing resin 54 is vertically applied along a side 56a of the electronic component 56 (for example, from a point on the substrate 53 to the upper part of the side of the electronic component 56). This may concentrate the stress b at the joint 55 between the reinforcing resin 54 and the substrate 53, at the bottom of the reinforcing resin 54, thereby separating the reinforcing resin 54 from the substrate 53 so as to deteriorate the reinforcing function.
For such a large electronic component, in a proposed structure as shown in FIG. 31, a reinforcing component 61 shaped along the outside shape of the lower part of an electronic component 60 is fit onto the electronic component 60 from below and elastic protrusions 62 elastically in contact with the outer surface of the electronic component 60 are formed on the inner periphery of the reinforcing component 61 (for example, Japanese Patent Laid-Open No. 2001-102237). In this structure, however, the reinforcing component 61 needs to be fabricated again according to a size change of the electronic component 60, increasing the manufacturing cost and the number of manufacturing steps.
In another proposed method, a tying band for fixing an electronic component is used, a hole for insertion of the tying band is formed on a substrate, and the tying band is inserted into the hole so as to restrain the substrate and the electronic component, mechanically fixing the electronic component to the substrate (for example, Japanese Patent Laid-Open No. 10-233566). In this case, however, the hole for fixing the tying band needs to be formed on the substrate. This further limits the design with restricted applicability.
As has been discussed, in the mounting structure shown in FIGS. 30A to 30C, the reinforcing resin 54 is vertically applied along the side 56a of the electronic component 56 (that is, in the height direction of the electronic component 56) so as to reinforce the joint holding power of the electronic component 52 on the substrate 53. Advantageously, the mounting structure can easily respond to a change of the shape of the electronic component 56 only by changing the position of application of the reinforcing resin 54, whereas the mounting structure cannot obtain a sufficient reinforcing effect for the relatively large electronic component 56 joined to the substrate 53.
In the method using the structure and tying band of FIG. 31, a sufficient reinforcing effect can be obtained for the large electronic component 60 joined to the substrate. However, this method may increase the manufacturing cost and the number of manufacturing steps, further limiting the design with restricted applicability.
As has been discussed, the conventional mounting structure and method for an electronic component cannot simultaneously achieve the function of obtaining a sufficient reinforcing effect for a relatively large electronic component and the function of easily responding to a change of the shape of the electronic component.
The present invention has been devised to solve the problem. An object of the present invention is to provide a mounting structure and a method for supplying a reinforcing resin material, which can obtain a sufficient reinforcing effect for an electronic component, e.g., a large capacitor that is relatively thick in profile from a substrate, and easily respond to a change of the shape of the electronic component.